import 'package:flutter/material.dart';

/// 磁吸进度状态
class MagneticSnapState {
  /// 吸附进度 0.0 ~ 1.0
  final double progress;

  /// 媒体库透明度
  double get mediaOpacity {
    // 0% ~ 70%: 1.0 → 0.45
    // 70% ~ 100%: 0.45 → 0
    if (progress <= 0.7) {
      return 1.0 - (progress / 0.7) * 0.55;
    } else {
      final t = (progress - 0.7) / 0.3;
      return 0.45 * (1 - t);
    }
  }

  /// 收藏标题位移（从 +12px → 0）
  double get favoriteTranslateY {
    return (1 - progress) * 12;
  }

  /// 收藏列表展开程度 0.0 ~ 1.0
  double get listReveal {
    if (progress <= 0.7) return 0.0;
    return (progress - 0.7) / 0.3;
  }

  /// 是否完全吸附
  bool get isSnapped => progress >= 1.0;

  /// 是否在磁吸区（进度 > 70%）
  bool get isInMagneticZone => progress > 0.7;

  const MagneticSnapState(this.progress);

  factory MagneticSnapState.initial() => const MagneticSnapState(0.0);

  MagneticSnapState copyWith({double? progress}) {
    return MagneticSnapState(progress ?? this.progress);
  }
}

/// 磁吸控制器
class MagneticScrollController extends ChangeNotifier {
  /// 吸附进度
  double _progress = 0.0;
  double get progress => _progress;

  /// 是否已吸附
  bool _isSnapped = false;
  bool get isSnapped => _isSnapped;

  /// 动画控制器（用于吸附动画）
  AnimationController? _animationController;
  TickerProvider? _tickerProvider;

  /// 状态
  MagneticSnapState get state => MagneticSnapState(_progress);

  void init(TickerProvider vsync) {
    _animationController = AnimationController(
      vsync: vsync,
      duration: const Duration(milliseconds: 300),
    );
  }

  @override
  void dispose() {
    _animationController?.dispose();
    super.dispose();
  }

  /// 更新滚动进度（在滚动时调用）
  void updateProgress(double newProgress) {
    if (_isSnapped) return;
    _progress = newProgress.clamp(0.0, 1.0);
    notifyListeners();
  }

  /// 处理松手事件
  void onDragEnd(double velocity) {
    if (_isSnapped) return;

    final threshold = 0.45; // 45% 触发吸附
    final shouldSnap = _progress > threshold || velocity > 800;

    if (shouldSnap) {
      snapOpen();
    } else {
      snapBack();
    }
  }

  /// 吸附展开
  void snapOpen() {
    if (_isSnapped) return;
    _isSnapped = true;

    _animationController?.reset();
    _animationController
        ?.animateTo(
      1.0,
      duration: const Duration(milliseconds: 300),
      curve: Curves.easeOutBack,
    )
        .then((_) {
      _progress = 1.0;
      notifyListeners();
    });

    // 实时更新进度
    _animationController?.addListener(() {
      _progress = _animationController!.value;
      notifyListeners();
    });
  }

  /// 回弹
  void snapBack() {
    if (_isSnapped) return;

    _animationController?.reset();
    _animationController
        ?.animateTo(
      0.0,
      duration: const Duration(milliseconds: 250),
      curve: Curves.easeOut,
    )
        .then((_) {
      _progress = 0.0;
      notifyListeners();
    });

    _animationController?.addListener(() {
      _progress = _animationController!.value;
      notifyListeners();
    });
  }

  /// 重置状态（退出页面时）
  void reset() {
    _isSnapped = false;
    _progress = 0.0;
    _animationController?.reset();
    notifyListeners();
  }
}